Recently, portable telephones have come into wide use. In the beginning, portable telephones, the shapes of which were longitudinally long, were mainly used. However, in order to enhance the portability of portable telephones by reducing the length, folding type portable telephones are mainly used in which the housing of each portable telephone is divided into an upper housing and a lower housing, and the divided upper and lower housings are placed on each other and opened and closed by being rotated around a rotary shaft arranged on one end of the upper and lower housings.
When the folding type portable telephone is carried by a user, it is folded. When the user makes a phone call, the portable telephone is extended so that a microphone and a receiver of the portable telephone can be brought close to the ear and the mouth of the user to utilize the acoustic characteristic of the portable telephone. However, the functions of portable telephones have recently multiplied. Portable telephones have recently come into wide use which have an internet connecting function, a digital camera function shown in JP-A-2003-179678 and a television function in addition to a mail function by which characters or photographs are sent to another party's portable telephone. Further, portable telephones having a finger print authentication function, which is shown in Patent Document 1, have been developed. Therefore, in addition to the functions used when the folded housings are opened, the number of functions, which can be used even when the folded housings are closed, is increasing.
Concerning the form in which the length of the portable telephone is reduced, except for the aforementioned form in which the upper and lower housings are folded, a rotary form is provided in which a rotary shaft is arranged perpendicularly to a face on which the upper and the lower housing are placed on each other and the upper housing is rotated with respect to the lower housing 180° around this rotary shaft so as to extend the length of the portable telephone. Further, a sliding form is provided in which the upper housing is slid with respect to the lower housing when sliding rails are arranged on the face on which the upper and the lower housing are placed on each other or when a tunnel structure is provided on the face on which the upper and the lower housing are place on each other. Concerning this form, refer to JP-A-2003-179678 and JP-A-2003-32335.
In these sliding portable telephones, in the portable telephone in which the upper and the lower housing are connected to each other by sliding rails, in order to prevent the sliding rails and the upper and the lower housing from being separated from each other, a structure is provided by which the upper housing is prevented from being drawn out from the sliding rails in the sliding rail moving direction. Concerning this structure, refer to JP-A-2003-179678. This sliding structure is convenient for the user of the portable telephone since the portable telephone can be used both at a short length (i.e. not fully slid) and at a long length (i.e. fully slid) according to the situation, that is, this sliding structure effectively widens the usage of the portable telephone.    JP-A-2003-179678: Japanese Patent Unexamined Publication No. 2003-179678 (Refer to reference numerals 104 and 105 in FIG. 2)    JP-A-2003-179678: Japanese Patent Unexamined Publication No. 2003-179678 (Refer to FIGS. 3 and 4 and the explanations)    JP-A-2003-32335: Japanese Patent Unexamined Publication No. 2003-32335 (Refer to FIGS. 1 and 2 and the explanations)